A traditional fluorescent lamp generates a light by ionization of gas enclosed within the lamp, which allows a high electrical current to flow through the lamp. Typically a fluorescent lamp is connected with a ballast, which serves to limit the current flowing through the lamp. Without the ballast, a fluorescent lamp connected directly to a high voltage power source can rapidly and uncontrollably increase its current draw, which can then lead to overheating and eventual destruction of the lamp.
On the other hand, illumination devices based on semiconductor light sources, such as light-emitting diodes (LED), offer many advantages over traditional fluorescent lighting system, such as higher energy efficiency and longer expected lifetime. But LED requires a precise amount of a direct current (“DC”) supply. This creates a problem when people try to reuse the existing fluorescent lighting fixture, which includes the socket for the lamp as well as the ballast. Simply replacing the fluorescent lamp with a LED lamp would not work, because the ballast may provide an alternating current (“AC”) that is not precisely controlled to the LED lamp, due to various factors such as a ballast circuit design, a device variation, a voltage variation, temperature dependency, etc. As a result, typically LED lamps are not compatible with existing systems designed for fluorescent lights, and extra rewiring is needed to remove or to bypass the ballast, before the existing systems can be used for LED lamps. On the other hand, these LED lamps can be fully compatible with systems designed solely for LED lights that do not include ballast. However, for such a system, there is still a need to precisely control the current supplied to the LEDs within the lamps to control the intensity of light generated by the LEDs.
Therefore, there is a need for an LED lamp with a flexible lighting driver that works with and without a ballast, which allows easy retrofitting LED lamps into existing fluorescent lamp lighting fixtures as well as LED fixtures, while providing precise control of intensity of lights provided by the LED lamps.